Image converter tubes



-Feb- 18, i958 c. s. szEGHo ETAL 2,324,247

IMAGE CONVERTER TUBES linearer. 19, 194e v Stwenfors CONSTANT/N 5. SZEGHU u//LL/AM a R551) (lttomeg- Unite IMAGE CONVERTER TUBES Constantin S. Szegho and William 0. Reed, Chicago, Ill., assignors to The Rauland Corporation, Chicago, Ill., a corporation of Illinois Application February 19, 1948, Serial No. 9,497

4 Claims. (Cl. 313-65) This invention relates to new and useful improvements in electronic storage devices.

The object of the invention is an image converter which stores the intelligence impressed on its photoelectric cathode and makes it visible on its fluorescent screen when desired.

The invention will more clearly appear from the claims and the description of an embodiment and its storage electrode diagrammatically illustrated in Figs. l, 2 and 3 of the drawing.

In Fig. l the device is enclosed within evacuated envelope having a cylindrical body 1 and an oblique hollow branch 2 opening into the body approximately midway between its ends. An end wall 3 of cylinder 1 carries a iiuorescent screen 4 covered by an aluminum lm 5 which also contacts the side of the cylinder.

The closed end of branch 2 is convex and carries a photocathode 6 on which intelligence signals may be impressed, e. g. by infra-red rays. Negative potential of 600 volts may be applied to cathode 6. The photoelectrons released by the photocathode are by means of electron lenses 7 and 7 accelerated and focused on insulating surface 8 of a storage electrode. The storage electrode is mounted parallel with the screen 4 in the cylinder 1 and consists of secondary emittive insulating surface 8 such as silica or barium fluoride evaporated onto a metal mesh 9. Figs. 2 and 3 illustrate the storage electrode in detail. Corresponding to the intelligence, more or less positive or negative charges will be produced on top of the insulator, the polarity of which depends on the accelerating voltages of electrodes 7 and 7 which may be respectively at negative potential of 200 volts and at ground potential. Secondary electrons which leave insulating surface 8 are collected by electrode 13. The potential of this electrode is preferably lowered during storing below 4000 volts which is used during transmission of the intelligence to uorescent screen 4. 'I'he lowering of the voltage applied to electrode 13 has two beneficial effects: (1) the secondary electrons are prevented from striking the uorescent screen and (2) the electrons from photocathode 6 are not appreciably deected from their path toward 8.

The charge stored on insulating surface 8 can be read 0n screen 4 by ooding mesh 9 with a. beam of electrons rice from an electron gun mounted near the right hand end of cylinder 1. The gun comprises a cathode 10 to which negative potential of 500 volts may be applied and accelerating and focusing electrode 11 and conductive coating 12 to which negative potential of 400 volts and ground may be respectively applied. Positive potentials of 8000 volts and 4000 volts are respectively applied to aluminum film 5 and electrode 13.

The number of electrons that pass through a unit area of the storage electrode depends on the positive charge existing thereon, and, therefore, on the intelligence conveyed by photocathode 6. The primary electrons that pass through the storage electrode are accelerated and focused on screen 4 by electron lens means 11 and 12. Due to the cylindrical nature of the arms, electromagnetic focusing may readily be applied to any of the sections. For instance, a coil placed around the left arm of cylindrical body 1 may be used to focus the electrons modulated by the stored signal on 8 onto the screen 4.

What is claimed is:

1. An electronic storage device comprising an evacuated envelope having a cylindrical body with a branch opening into the central part of the body, a fluorescent screen on one end of the cylinder, a source of electrons in the other end of the cylinder, a storage electrode in the cylinder adjacent the branch opening, said storage electrode having a metal mesh facing said source and an insulator deposited on it facing the fluorescent screen, means to accelerate and focus the electron stream passing through the mesh onto the fluorescent screen, a photocathode in the branch and means for accelerating and focusing the output of the photocathode on the insulator.

2. An electronic storage device comprising an evacuated envelope having a cylindrical body, an oblique hollow branch opening into the central part of the body and having a convex end, a fluorescent screen on the inside of one end of the cylinder, a gun in the other end of the cylinder for discharging a beam of electrons, an aluminum lm coating the screen and contacting with the adjacent side walls of the cylinder, a storage electrode parallel with the screen and positioned approximately midway in the cylinder adjacent the branch opening, said storage electrode having a metal mesh facing the gun and a mosaic of photosensitive particles facing the screen, a photocathode on the convex end of the branch and means for accelerating and focusing the output of the photocathode onto the mosaic.

3. The device according to claim 1, and in which the insulator consists of silica.

4. The device according to claim 1, and in which the insulator consists of barium uoride.

References Cited in the tile of this patent UNITED STATES PATENTS 2,142,609 Kessler Ian. 3, 1939 2,258,294 Lubszinski et al. Oct. 7, 1941 2,306,272 Levy Dec. 22. 1942 

